The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Network devices such as routers and switches may process and forward network traffic according to configurable settings. The traffic may be transmitted from device to device on a network of the devices, often on behalf of applications communicating on the network. Individual items of traffic may be transmitted as packets along a route from a source application, service, or device to a destination application, service, or device.
Network administrators may configure network devices on the network such that the devices operate together to accomplish certain objectives. The objectives may include performance goals for applications, services, or devices using the network. For example, a network of devices may be configured to give priority to certain types of traffic, deter or prevent attacks against the network, save power, minimize latency, minimize the effects of applications, services, or devices that are overusing bandwidth, or meet levels of service that are guaranteed by a service provider under service agreements. In a particular example, the network administrator may guarantee levels of service for voice over Internet Protocol (“VoIP”) applications or other business-critical applications so that application users can obtain the full benefit of the applications.
Passive monitoring may provide some information about production traffic on the network. However, due to privacy and security concerns, as well as legal issues stemming from those concerns, network administrators may be limited in terms of the amount of passive monitoring that can be performed on production traffic. Also, passive monitoring may not provide enough information when there is little or no relevant production traffic.
To determine whether network devices are meeting the demands of various applications, services, or devices, the network administrator may actively monitor the network by placing physical probes between devices in the network. The physical probes generate test traffic as if the test traffic was generated by particular applications, services, or devices using the network. The privacy and security concerns may be avoided by active monitoring because the generated test traffic is synthetic.
Some network devices are equipped with logic, in hardware, software, or a combination of hardware and software such as that provided on devices running Cisco IOS® Software, which allows the network administrator to use the network devices to create logical probes without adding any physical probes to the network. In a particular example, with Cisco IOS® Software an Internet Protocol Service Level Agreement (IPSLA) is a feature that allows network administrators to actively monitor and analyze IP service levels for IP applications and services.
The probes may generate the test traffic in a predictable manner even when the applications, services, or devices using the network are generating production traffic in an unpredictable manner. As a result of sending test traffic and receiving responses to the test traffic, active network monitoring provides a more detailed understanding of how the network is performing with respect to an application, service, or device.
Network administrators use probes sparingly so that the generated test traffic does not substantially slow down the network. If an application was not actively tested during a relevant period, a network administrator may not have enough information to troubleshoot how the network is handling the application. Alternately, the network administrator may not be able to confirm that the network is handling the particular application in accordance with existing service level agreements.